Messages in this thread | | | Date | Mon, 21 Jan 2008 17:08:05 -0800 | From | "H. Peter Anvin" <> | Subject | Re: W1: w1_slave units, standardize 1C or .001C? Break API |
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David Fries wrote: > The ds18b20 one wire temperature sensor conversion routine is > returning the units in degrees C while the ds1820 (ds18s20) is > returning it in .001 degrees C. 20C vs 20312C. Once you know the > units I'm liking the latter as it gives a higher precision. Time to > break user applications so the driver can give the temperature in the > same units for both sensors. > > I only have the ds18b20 sensor model. Here is the current output from > the sys file for this sensor. > /sys/devices/w1_bus_master1/28-0000000e84a2/w1_slave > 45 01 4b 46 7f ff 0b 10 84 : crc=84 YES > 45 01 4b 46 7f ff 0b 10 84 t=20 > > I ran the example data from the specification for the ds1820 through > it's conversion routine and found that t= was 1000 times the value. > What should the displayed units be? > > This is the same ds18b20 conversion *1000. Is everyone ok or is any > objecting to .001 degrees C for the units? Patch will follow. The > .001 C does truncate one bit of precision from the ds18b20 by the way. >
Millikelvins would have the nice property of never being negative. :)
-hpa
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